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Dwarf surf clam, Mulinia lateralis. Photograph Jax Shells.

Species Name: Mulinia lateralis Say, 1822
Common Name: Dwarf Surf Clam
Coot Clam
Synonymy: None

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Animalia Mollusca Bivalvia Veneroida Mactridae Mulinia

    Species Description

    Mulinia lateralis is a small opportunistic bivalve in the family Mactridae. The exterior of the shell is cream to yellowish-orange while the interior is bright white.


    Regional Occurrence

    Mulinia lateralis has a broad geographic range that extends from New Brunswick, NJ to the Yucatan in Mexico (Levinton 1971). The dwarf surf clam is normally found in the soft strata in benthic communities.

    IRL Distribution

    Mulinia lateralis occurs in the Indian River Lagoon.


    Age, Size, Lifespan

    Mulinia lateralis can live up to two years (Lu et al. 1996). Adults are approximately 15 to 20 mm in length while newly metamorphosed juvenile shell lengths range from 200 to 700 µm (Yongping and Guo 2008). The dwarf surf clam has a short generation time reaching sexual maturity in 1-2 months (Guo and Allen 1994).


    Mulinia lateralis can reach average densities of up to 21,000 individual per m2 (Santos and Simon 1980). It is an opportunistic species that grows and reproduces quickly becoming dominant in areas where conditions are optimal (Chlaermwat et al. 1991).


    The dwarf surf clam has separate sexes (Lu et al. 1996). Mature adults spawn from May to November. A female will usually release between 0.5 to 2 million eggs during a spawning event (Lu et al. 1996). In the laboratory, individuals produced 3 x 105 eggs or 2.5 x 109 sperm cells (Guo and Allen 1994).


    Mulinia lateralis has pelagic planktotrophic larval stages that lives in the plankton from 7-22 days (Mann et al. 1991). Settlement occurs after the larvae reach the pediveliger stage, developing a hinged shell and a foot.



    The development of fertilized eggs from the dwarf clam is greatly reduced at temperatures below and above 20-25°C (Calabrese 1969).


    Adult Mulinia lateralis occurs in estuaries where the salinity varies from 18 to 30 ppt (Lippson and Lippson 1984). In laboratory experiments, embryos exhibited a high tolerance for salinity changes developing into normal straight-hinge larvae over a wide range of salinities 15 to 35 ppt (Calabrese 1969).


    Trophic Mode

    Mulinia lateralis is a filter feeder, feeding mainly on suspended bacteria (Chalermwat et al. 1991).


    Crabs are a major predator of M. lateralis. Predation is probably the major factor controlling adult population size, at least during warmer months (Virnstein 1979).


    Economic/Ecological Importance

    Mulinia lateralis numbers increase drastically in the absence of predators.


    Calabrese A. 1969. Individual and combined effects of salinity and temperature on embryos and larvae of the coot clam, Mulinia lateralis (Say). Biological Bulletin 137:417-428.

    Chalermwat K, Jacobson TR, and RA Lutz. 1991. Assimilation of bacteria by the dwarf surf clam Mulinia lateralis (Bivalvia: Mactridae). Marine Ecology Progress Series 71:27-35.

    Guo X and SK Allen, Jr. 1994. Sex determination and polyploidy gigantism in the dwarf surfclam (Mulinia lateralis Say). Genetics 138:1199-1206.

    Levinton JS. 2001. Genetics, Paleontology, and Macroevolution. Cambridge University Press, pg. 114.

    Lippson AJ and RL Lippson. 1984. Life in Chesapeake Bay. John Hopkins University Press, Baltimore.

    Lu JK, Chen TT, Allen SK, Matsubara T, and JC Burns. 1996. Production of transgenic dwarf surfclams, Mulinia lateralis, with pantropic retroviral vectors. Proceeding of the National Academy of Sciences 93:3482-3486.

    Mann R, Campos BM, and MW Luckenbach. 1991. Swimming rate and responses of larvae of three mactrid bivalves to salinity discontinuities. Marine Ecology Progress Series 68:257-269.

    Santos SL and JL Simon. 1980. Response of soft-bottom benthos to annual catastrophic disturbance in a South Florida estuary. Marine Ecology Progress Series 3:347-355.

    Virnstein RW. 1979. Predation on Estuarine Infauna: Response Patterns of Component Species. Estuaries (2) 2: 69-86.

    Yongping W and X Guo. 2008. Chromosomal mapping of the major ribosomal RNA genes in the dwarf surfclam. Journal of Shellfish Research 27:307-311.

Report by: Melany P. Puglisi and Maribel Thiebaud, Smithsonian Marine Station
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Page last updated: October 1, 2008

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